Im going to set aside the last part of your question, whether it matters to the morality of looking at the images in question that those depicted are (sometimes) dead. That raises a collection of issues that it would take some time to address (a number of responses on this site under the topic 'Death' may be helpful to you: http://askphilosophers.org/topic/economics?topic=239).
So is there anything morally objectionable at looking at the images of Abu Ghraib or of nude celebrities? My sense is that they raise rather different sets of moral issues. The Abu Ghraib images, for one, depict actions undertaken by government representatives (soldiers) in the course of a military conflict. Their release to the public seems to promote a good (knowing what our military is doing) that clearly doesn't apply to nude celebrities. To use a legal idiom, there is no compelling public interest at stake in disseminating nude celebrity photos. So if there is a moral case against looking at the Abu Ghraib images, it seems...